This invention relates to an assembly and a method for fastening a stent onto a catheter. This kind of device finds routine use in the area of percutaneous transluminal coronary angioplasty (PTCA) procedures, although it may be used in other types of procedures, as well.
Stents and stent delivery assemblies are utilized in a number of medical procedures and situations, and as such their structure and function are well known. A stent is a generally cylindrical prosthesis introduced via a catheter into a lumen of a body vessel in a configuration having a generally reduced diameter and then expanded to the diameter of the vessel. In its expanded configuration, the stent supports and reinforces the vessel walls while maintaining the vessel in an open, unobstructed condition.
Inflation expandable stents are well known and widely available in a variety of designs and configurations. Inflation expandable stents are crimped to their reduced diameter about the delivery catheter, then maneuvered to the deployment site and expanded to the vessel diameter by fluid inflation of a balloon positioned between the stent and the delivery catheter. The present invention is particularly concerned with the crimping of inflation expandable stents although self-expanding stent may be used as well.
An example of an inflation expandable stent is described in PCT Application No. 960 3092 A1, published Feb. 8, 1996, the content of which is incorporated herein by reference.
In advancing an inflation expandable balloon through a body vessel to the deployment site, the stent must be able to securely maintain its axial position on the delivery catheter, without translocating proximally or distally, and especially without becoming separated from the catheter. Stents that are not properly secured or retained to the catheter may slip and either be lost or be deployed in the wrong location or partially deployed. The stent must be crimped in such a way as to minimize or prevent altogether distortion of the stent and to thereby prevent abrasion and/or reduce trauma of the vessel walls. The stent must also be crimped in such a way as to avoid damaging the balloon.
In the past, crimping has been done by hand often resulting in the application of undesired uneven forces to the stent. Such a stent must either be discarded or re-crimped. Stents which have been crimped multiple times can suffer from fatigue and may be scored or otherwise marked which can cause thrombosis. A poorly crimped stent can also damage the underlying balloon.
Recently, stent crimping devices have been disclosed in U.S. Pat. No. 5,546,646 to Williams et al, U.S. Pat. No. 5,183,085 to Timmermans et al., U.S. 5,626,604 to Cottone, Jr., U.S. Pat. Nos. 5,725,519, 5,810,873 to Morales, WO 97/20593 and WO 98/19633.
There remains a need to produce a device, optionally portable, to crimp a stent onto a catheter uniformly or reduce a stent in diameter while minimizing the distortion of and scoring and marking of the stent and due to the crimping or size reduction.
In the description that follows it is understood that the invention contemplates crimping a stent either directly to a catheter tube or to a catheter balloon which is disposed about a catheter tube. When reference is made to crimping a stent to a catheter, a balloon may be situated between the stent and the catheter tube or the stent may be crimped to a region of a catheter tube directly.
All U.S. patents and applications and all other published documents mentioned anywhere in this application are incorporated herein by reference in their entirety.
The present invention is directed to an apparatus for reducing a medical device such as a stent in size. The apparatus includes a plurality of jaw-like dies which may be closed inward on the stent to apply an inward directed crimping force to the stent. The dies may be arranged directly opposite one another or may be interleaved. The dies may also be disposed in other configurations as well. A stent may be reduced in size by placing it between the jaw-like dies and moving the dies inward to apply an inward force to the stent. The dies may be moved inward manually or by the use of a suitable actuation device such as an air cylinder or a pneumatic screw.
In one embodiment, the invention is directed to an apparatus for reducing a medical device in size comprising at least one first crimping die with a first crimping surface for contacting the medical device and at least one second crimping die with a second crimping surface for contacting the medical device. The apparatus further comprises a crimping die moving device which connects the first and second crimping dies. The crimping die moving device is constructed and arranged to move the first and second crimping dies toward one another from an open position to a closed position. In the open position, the first and second crimping dies are spaced to form an opening in which a medical device may be inserted. In the closed position, the first and second crimping dies form an opening of reduced size.
In another embodiment, the invention is directed to a stent crimper comprising at least a first crimping die having a first notch therein forming a crimping surface and at least a second crimping die having a projecting portion with a second notch therein forming a crimping surface. The projecting portion is sized to fit at least a part of the way into the first notch in the first crimping die. The crimper further comprises a base portion constructed and arranged to movably receive the first and second dies. The first and second dies are movably received on the base portion with the first and second notches facing each other so as to form a variable size stent receiving region. The first and second crimping dies are movable from an open position in which a stent may be received between the first and second notches to a closed position in which a crimping force is applied to the stent.
In yet another embodiment, the invention is directed to a stent crimper comprising a plurality of linearly arranged, spaced first and second crimping dies. Each first crimping die has a first notch therein forming a crimping surface. Each second crimping die has a second notch therein forming a crimping surface. The crimper further comprises a base portion constructed and arranged to movably receive the first and second crimping dies. The first and second crimping dies are movable from an open position in which a stent may be received between the first and second notches to a closed position in which the first and second crimping dies are interleaved and a crimping force is applied to the stent.
In yet another embodiment, the invention is directed to a stent crimper comprising a plurality of linearly arranged, spaced first crimping dies and linearly arranged, spaced second crimping dies. Each first crimping die has a first notch therein which forms a crimping surface and each second crimping die has a second notch therein which forms a crimping surface. A connecting member connects first and second crimping dies. The first and second crimping dies are movable from an open position in which a stent may be received between the first and second notches to a closed position in which the first and second crimping dies are interleaved and a crimping force is applied to the stent.
In yet another embodiment, the invention is directed to a stent crimper comprising a plurality of linearly arranged die sets which are linearly spaced apart from one another. Each die set comprises a plurality of crimping dies disposed about an open region. Each of the dies in a given die set are disposed radially about a common point, and are movable from an open position in which the open region is sized to receive a stent therethrough to a closed position in which the dies apply a crimping force to the stent. The crimper further comprises at least one actuation device. Each die set is in communication with an actuation device, which may separately control individual dies sets, moving the dies from the open position to the closed position.
In yet another embodiment, the crimper comprises a multiplicity of dies which are disposed at various angles about the longitudinal axis of the stent.
The invention is also directed to a method for reducing a stent or other medical device in size using the inventive apparatus. The medical device is placed in the apparatus in between the first and second crimping dies and the first and second crimping dies moved relatively closer together. An inward force is applied to the medical device thereby reducing the medical device in size. The stent may be placed in a protective sleeve prior to crimping.
The invention also contemplates reducing a stent in size using an inventive crimper as a step in a multistep size reduction and crimping process. A stent may be reduced somewhat in size using any other suitable size reduction technique and then crimped on to a catheter using the inventive apparatus. In one such method, the stent is initially reduced in size by placing it in a braid or other suitable sleeve and elongating the sleeve with a resulting reduction in diameter. The stent is then placed in the inventive apparatus and further reduced in size. Alternatively, the inventive apparatus may be used as a first step in reducing a stent in size prior to crimping the stent onto a catheter.